Data storage media

ABSTRACT

The data storage media comprises, in a preferred embodiment, a homogenous or non-homogenous plastic substrate that can be formed in situ with the desired surface features disposed thereon on one or both sides, a data storage layer such as a magneto-optic material also on one or both sides, and an optional protective, dielectric, and/or reflective layers. The substrate can have a substantially homogenous, tapered, concave, or convex geometry, with various types and geometries of reinforcement employed to increase stiffness without adversely effecting surface integrity and smoothness.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation application of U.S. patentapplication Ser. No. 09/502,968 filed Feb. 11, 2000, and also claims thebenefit of the filing date of U.S. Provisional Application Ser. Nos.60/120,101 filed Feb. 12, 1999, Attorney Docket Nos. GP2-0001 and8CN-8803PA; 60/134,585 filed May 17, 1999, Attorney Docket No.8CN-8807PA; 60/137,883 filed Jun. 7, 1999, Attorney Docket No.8CU-5845PA; 60/137,884 filed Jun. 7, 1999, Attorney Docket Nos.8CU-5846PA; and 60/146,248 filed Jul. 29, 1999, Attorney Docket No.8CN-8826PA and GP2-0018; the entire contents of each application arehereby incorporated by reference.

BACKGROUND OF INVENTION

[0002] Optical, magnetic and magneto-optic media are primary sources ofhigh performance storage technology that enables high storage capacitycoupled with a reasonable price per megabyte of storage. Areal density,typically expressed as billions of bits per square inch of disk surfacearea (Gbits per square inch (Gbits/in ²)), is equivalent to the lineardensity (bits of information per inch of track) multiplied by the trackdensity in tracks per inch. Improved areal density has been one of thekey factors in the price reduction per megabyte, and further increasesin areal density continue to be demanded by the industry.

[0003] In the area of optical storage, advances focus on access time,system volume, and competitive costing. Increasing areal density isbeing addressed by focusing on the diffraction limits of optics (usingnear-field optics), investigating three dimensional storage,investigating potential holographic recording methods and othertechniques.

[0004] Conventional polymeric data storage media has been employed inareas such as compact disks (CD-ROM) and recordable or re-writablecompact disks (e.g., CD-RW), and similar relatively low areal densitydevices, e.g. less than about 1 Gbits/in², which are typicallyread-through devices requiring the employment of a good optical qualitysubstrate having low birefringence.

[0005] Referring to FIG. 1, a low areal density system 1 is illustratedhaving a read device 3 and a recordable or re-writable storage media 5.The storage media 5 comprises conventional layers, including a datalayer 7, dielectric layers 9 and 9′, reflective layer 11, and protectivelayer 13. During operation of the system 1, a laser 15 produced by theread device 3 is incident upon the optically clear substrate 17. Thelaser passes through the substrate 17, and through the dielectric layer9, the data layer 7 and a second dielectric layer 9′. The laser 15 thenreflects off the reflective layer 11, back through the dielectric layer9′, the data layer 7, the dielectric layer 9, and the substrate 17 andis read by the read device 3.

[0006] Unlike the CD and beyond that of the DVD, storage media havinghigh areal density capabilities, typically greater than 5 Gbits/in²,employ first surface or near field read/write techniques in order toincrease the areal density. For such storage media, although the opticalquality of the substrate is not relevant, the physical and mechanicalproperties of the substrate become increasingly important. For highareal density applications, including first surface applications, thesurface quality of the storage media can affect the accuracy of thereading device, the ability to store data, and replication qualities ofthe substrate. Furthermore, the physical characteristics of the storagemedia when in use can also affect the ability to store and retrievedata; i.e. the axial displacement of the media, if too great, caninhibit accurate retrieval of data and/or damage the read/write device.

[0007] Conventionally, the above issues associated with employing firstsurface, including near field, techniques have been addressed byutilizing metal, e.g., aluminum, and glass substrates. These substratesare formed into a disk and the desired layers are disposed upon thesubstrate using various techniques, such as sputtering. Possible layersinclude reflective layers, dielectric layers, data storage layers andprotective layers. Once the desired magnetic layers have been added, thedisk may be partitioned into radial and tangential sectors throughmagnetic read/write techniques. Sector structure may also be addedthrough physical or chemical techniques, e.g. etching, however this mustoccur prior to the deposition of the magnetic layers.

[0008] As is evident from the fast pace of the industry, the demand forgreater storage capacities at lower prices, the desire to havere-writable disks, and the numerous techniques being investigated,further advances in the technology are constantly desired and sought.What is needed in the art is advances in storage media substratematerials enabling storage media to be utilized in first surface,including near field, applications.

TECHNICAL FIELD

[0009] The present invention relates to data storage media, andespecially relates to methods of making data storage media and topartially and wholly polymeric data storage media.

SUMMARY OF INVENTION

[0010] The present invention relates to data storage media as well asmethods for making and processes for using the same. In some preferredembodiments, the storage media comprises: a substrate comprised of atleast one plastic resin portion, and at least one data layer on thesubstrate wherein the data layer can be at least partly read from,written to, or a combination thereof by at least one energy field, andwherein when the energy field contacts the storage media said energyfield is incident upon the data layer before it could be incident uponthe substrate.

[0011] In another embodiment, the data storage media comprises: a rigidsubstrate, a plastic layer comprising surface features, and at least oneadditional layer on the plastic layer. The plastic layer preferably ismade from a resin capable of withstanding various techniques, such assputtering, for additional desired layers including, e.g., reflectivelayers, dielectric layers, data storage layers, and protective layers.The surface features present in the plastic layer are preferablyembossed surface features and the plastic layer has preferably beenapplied to the substrate using spin coating, and/or spray coatingtechniques. In another embodiment, the method comprises: forming aplastic substrate followed by forming a data storage layer onto thesubstrate. The method can comprise introducing a molten polymer to amold to make a plastic substrate; cooling said plastic substrate; andforming a data storage layer onto said plastic substrate. The method canoptionally comprise forming geographic locators on at least one side ofsaid plastic substrate in situ. The method may also optionally compriseforming the data storage layer over the geographic locators.

[0012] In yet another embodiment, the method of storing data comprises:rotating a storage media comprising a substrate having at least aplastic portion and at least one data layer disposed on at least onesurface of said substrate; directing an energy field at said storagemedia such that said energy field is incident upon the datalayer beforeit can be incident upon the substrate; and retrieving information fromthe data storage layer. A variety of energy fields could be employed,e.g., magneto-optic storage wherein a magnetic field and/or opticallaser are used to write but an optical beam utilizing reflecting opticsis used to read.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 is a cross-sectional illustration of a prior art low arealdensity system employing an optically clear substrate.

[0014]FIG. 2 is a cross-sectional illustration of a read/write systemusing one possible embodiment of a storage media of the presentinvention with a light incident on the data storage layer withoutpassing through the substrate.

[0015]FIG. 3 is a cross-sectional illustration of one embodiment of amagnetic data storage substrate of the present invention.

[0016]FIG. 4 is a graph of flexural modulus versus specific gravity forvarious fundamental axial modal frequencies of a monolithic disk havinga 95 mm outer diameter by 0.8 mm thickness.

[0017]FIG. 5 is a graph of specific stiffness (flexural modulus dividedby specific gravity) versus damping coefficient for various peak-to-peakaxial displacements when excited by a 1 G sinusoidal load.

[0018]FIG. 6 is a graph representing the fundamental axial modalfrequency for a multi layered composite 130 mm outer diameter by 1.2 mmthickness disk with homogeneous layers of neat and reinforced polymer.

[0019]FIG. 7 is graph representing axial displacement peak to peak fromvibration at the first fundamental frequency for a multi-layeredcomposite (ABA co-injected disk) 130 mm outer diameter by 1.2 mmthickness disk having homogeneous layers of neat and reinforced polymer.

[0020] FIGS. 8 to 21 illustrate various cross-sectional and top views ofembodiments of the present invention having a core/insert of material,or hollow or filled cavities, with the core/insert disposed at variouslocations, with various geometries.

[0021]FIG. 22 is an embodiment similar to FIG. 19 illustrating anon-homogenous (ABA) substrate with pits or grooves.

[0022]FIGS. 23 and 24 are cross-sectional views of additionalembodiments of the present invention illustrating a substrate havingthin plastic film.

[0023]FIG. 25 is a cross-sectional view of one embodiment of atri-component disk of the present invention.

[0024]FIG. 26 is a cross-sectional view of another embodiment of a diskof the present invention secured with a clamp.

[0025]FIG. 27 is a cross-sectional view of yet another embodiment of thepresent invention having a thin plastic film disposed on a portion of acore.

[0026] FIGS. 28 to 32 illustrate various embodiments of possiblesubstrate geometries for the substrate of the present invention.

[0027] FIGS. 33 to 35 illustrate various embodiments of possible coregeometries for the storage media of the present invention.

[0028]FIG. 36 illustrates modal shapes obtained from with a 130 mm diskvia chirp excitation.

[0029] The above described Figures are meant to be exemplary, notlimiting, merely illustrating some of the potential embodiments of thepresent invention.

DETAILED DESCRIPTION

[0030] The data storage media is partially or wholly comprised of aplastic material. This storage media is useful in high areal densityapplications, first surface and similar applications, wherein an energyfield incident on the data storage layer(s) contacts the data storagelayer(s) without or at least prior to contacting the substrate. In otherwords, in contrast to conventional compact disks (CDs) and similarapplications, the energy field does not pass through the substrate tocontact the data storage layer or reflect back through the substrate tothe reading device. In order to function in such high areal densityapplications the storage media quality must exceed that of conventionalCDs and related media. The storage media, compared to conventional CDsand similar media, should have a reduced axial displacement when excitedby environmental and/or rotational vibrations, greater surface qualitydenoted by fewer irregularities or imperfections, and lower rotatingmoment of inertia (preferably about 5.5×10⁻³ slug-in² or less, withabout 4.5×10 ⁻³ slug-in² or less more preferred, and about 4.0 slug-in²or less especially preferred), among other qualities. Furthermore, thestorage media preferably comprises areal densities exceeding about 5Gbits/in², with greater than about 20 Gbits/in² more preferred, greaterthan about 50 Gbits/in² especially preferred, and up to or exceedingabout 100 Gbits/in² anticipated.

[0031] Generally, in high areal density applications, i.e. about 5Gbits/in² or greater, the read/write device is located relatively closeto the surface of the storage media (stand-off distance). In general,the higher the density sought, the closer the read/write device shouldbe to the surface of the storage media. Typically in these instances,the stand-off distance is generally less than about 0.3 millimeters(mm), and often less than about 760 nanometers (nm). For extremely highdensity, the read/write device is preferably extremely close, e.g., lessthan about 0.064 microns (μ), often less than about 0.013 μ from thesurface. Consequently, the axial displacement of the substrate should besufficiently less than a tolerable system deflection distance in orderto prevent damage to the read/write device and/or storage media surfaceduring vibration and/or shock conditions. For example, for a disk (130mm in outer diameter, 40 mm in inner diameter, and 1.2 mm in thickness)experiencing a sinusoidal gravitational loading of about 1 G, a resonantfrequency of about 170 Hz, and a stand-off distance of about 0.051 μ, anaxial displacement in peak to peak measurement of less than about 250 μis preferred, with less than about 150 μ more preferred, and less thanabout 125 μ especially preferred for instances when damage to thesubstrate and/or the read/write device is a primary concern. Preferably,an axial displacement in peak to peak measurement of about 500 μ orless, with about 250 μ or less preferred, is maintained to a shockmaximum of about 25 G's, with an about 2 to about 10 milliseconds (msec)application time and maintaining such a displacement to about 35 G'spreferred. However, in other instances, e.g., those with a largerstandoff distance (e.g., the about 0.30 μ or more stand-off) damage tothe head is not a dominating issue but rather, a very low axialdisplacement and/or disk tilt is preferred to allow for the optics toremain in focus since they may be incapable of responding to rapidchanges in focal length. The maximum radial tilt and tangential tilt areindependently about 1° or less, preferably, no more than about 1° each,and more preferably less than about 0.3° each, measured in a restingstate (i.e., not spinning).

[0032] The substrate axial displacement is a function of severalcharacteristics, including, but not limited to, the disk sizerequirements (inner and outer radii, and thickness), its stiffness(flexural modulus) and density, Poisson's ratio, loss modulus andstorage modulus, and combinations thereof and others. As the disk'souter radius increases, the axial displacement of the disk under shockand vibration conditions also increases, and as the disk thicknessdecreases, its sectional stiffness decreases while its axialdisplacement increases. Currently, the dimensions of the storage mediaare specified by the industry to enable their use in presently availablestorage media reading/writing devices. Consequently, the storage mediatypically has an inner diameter of up to about 40 millimeters (mm) andan outer diameter of up to about 130 mm or greater, with an innerdiameter of about 15 mm to about 40 mm and an outer diameter of about 65mm to about 130 mm generally employed. The overall thickness typicallyemployed is about 0.8 mm to about 2.5 mm, with a thickness up to about1.2 mm typically preferred. Other diameters and thicknesses could beemployed to obtain the desired architecture.

[0033] In addition to axial displacement, stiffness affects thefundamental frequencies for vibration of the substrate. It has beendetermined that the occurrence of the fundamental modal frequency can beadjusted based upon several factors, including material properties,e.g., the flexural modulus, thickness, and/or the specific gravity(S.G.)/density of the substrate or design architecture, e.g.internal/external stiffeners. (See FIG. 4) Since the modal frequenciesdefine the frequency at which the substrate naturally resonates,displacing the disk out of plane, it is preferred to have thesubstrate's first modal frequency outside of the storage media's normaloperating frequency. Normal operating frequencies are typically about 20Hz to about 500 Hz, with greater than 500 Hz anticipated for futureapplications. Consequently, the substrate preferably possesses aflexural modulus/density which places the first modal frequency outsideof the storage media's operating frequency. As is evident from FIG. 4(whose properties are set forth in the Table below) theinterrelationship of flexural modulus and specific gravity/densitygreatly effects the desired substrate flexural modulus and density.Preferably, the stiffness should be high and the density should be low.Typically, the flexural modulus should be about 250 thousand pounds persquare inch (kpsi) or greater, with a flexural modulus of about 350 kpsior greater preferred, about 500 kpsi or greater more preferred, and aflexural modulus of about 1000 kpsi or greater especially preferred,while the specific gravity is preferably about 1.5 or less, with aspecific gravity of about 1.3 or less more preferred, and a specificgravity of about 1.0 or less especially preferred.

[0034] As with the axial displacement, due to the small stand-offdistances employed and the deleterious effect of surface roughness oncarrier-to-noise ratio, the substrate should have a high surfacequality, particularly in the area of the storage media where the data isstored, and should be substantially flat to inhibit damage to theread/write device or surface of the storage media, and to enableaccurate data deposit and retrieval. Preferably, the substrate has atleast a portion of its surface with an average surface roughness((R_(a)) as measured by atomic force microscopy) of less than about 100Angstroms (Å), preferably with a roughness of less than about 10 Å, andmore preferably with a roughness of less than about 5 Å. (Roughness istypically an average of a 10 μ by 10 μ area of the substrate.) Themicrowaviness of the surface, which is typically an average of a 1 mm by1 mm area, can be up to about 100 Å, with up to about 10 Å preferred,and up to about 5 Å especially preferred. With respect to the flatness(also known as “run-out”), a substantially flat substrate essentiallyfree of ridges or valleys is especially preferred. A run-out of up toabout 100 μ can be employed, with a run-out of up to about 10 μpreferred, and a run-out up to about 5 μ especially preferred. (Flatnessis typically an average of the area of the entire disk.)

[0035] At such small stand-off distances, a ridge at or near the edge ofthe substrate, commonly known as edge-lift or ski-jump, can cause damageto the read/write device. The substrate should have a edge-lift heightof less than about 8 μ, with less than about 5 μ preferred, and lessthan about 3 μ especially preferred, with a edge-lift length of lessthan about 800 μ preferred, and less than about 500 μ especiallypreferred.

[0036] The storage media can be used in a variety of systems, some ofwhich will employ a restraining device necessitating consideration ofstiffness decay of the substrate. For a read/write system that employs aclamp, hub, or other restraining device to secure the storage media, thesubstrate should have a sufficient yield stress (at least in the contactarea of the restraining device) to avoid mechanical decay (both basedupon time and/or temperature). For a storage media having an outerdiameter of about 65 mm to about 130 mm, which will be secured within arestraining device of a read/write system, the plastic resins to be usedhave a preferred yield stress of about 7,000 psi or greater, with ayield stress exceeding about 9,000 psi especially preferred. In the caseof filled engineering plastic resins, higher yield stresses areobtainable, and yield stress exceeding about 10,000 pounds per squareinch (psi) are preferred, with greater than about 15,000 psi especiallypreferred.

[0037] Some such disks are illustrated in FIGS. 25 to 27. FIG. 25illustrates a disk 200 having a polymer surface 202, a filled or hollowcore 204, with a central portion 206 of a material comprising a higheryield stress than the plastic 202, such as a metal (e.g., aluminum),glass, ceramic, metal-matrix composite, and alloys and combinationscomprising at least one of the foregoing, and the like. FIG. 26illustrates a disk having a high yield stress central portion 206attached to a clamp 208. Meanwhile, FIG. 27 illustrates yet anotherembodiment wherein the polymer is a thin film over a core 204′ composedof the same material as the central portion 206. For example, the corecan be metal with a plastic film 202 disposed over a portion or all ofthe core.

[0038] Conventional substrates, e.g., aluminum and ceramic substrateswithout a plastic overlay, have a very high stiffness (e.g., aluminumwith a Young's modulus of about 70 gigapascals (GPa), and ceramic with aYoung's modulus of about 200 GPa), a level above that which has beenachieved with plastic substrates. It was unexpectedly found that thedamping coefficient of a material is important to offset the decreasedstiffness of plastic substrates as compared to aluminum. Consequently,in order to minimize effects of vibration of the disk, the visco-elasticmaterial properties of the substrate can be adjusted to enable dampingcapabilities. Vibration damping is achieved in a general sense, forexample, by inserting an appropriate spring/dashpot assembly between avibration source and an object to be vibrated. For effective damping,the material should absorb and/or dissipate the energy of vibrationtransmitted through the material as energy (e.g., heat energy) convertedas a result of planar shearing or bulk compression and expansion of thematerial.

[0039] For visco-elastic materials, such as plastic resins, there existsboth a storage modulus and a loss modulus. Storage modulus representselastic stiffness and loss modulus represents viscous stiffness. For astorage media having a stiffness less than aluminum, it is preferredthat the substrate have a mechanical damping coefficient (defined as theratio of the loss modulus over the storage modulus) of greater thanabout 0.04 at a temperature of 75° F. (about 24° C.), with greater thanabout 0.05 preferred, and greater than about 0.06 more preferred. Amechanical damping coefficient of greater than about 0.10 at atemperature of 75° F. is even more preferred, and a mechanical dampingcoefficient of greater than about 0.15 at a temperature of 75° F. isespecially preferred.

[0040] In addition, the damping properties of the material may beoptimized such that, for a frequency and temperature range of interest,the damping coefficient value does not drop below the desired value. Insome embodiments, the temperature range of interest and frequency rangefor applicability of the dampening is about 75° F. (24° C.) and about 2Hz to about 150° F. (65.5° C.) and about 400 Hz preferred, with about32° F. (0° C.) and about 2 Hz to about 200° F. (93.3° C.) and about 500Hz more preferred.

[0041] FIGS. 5 and 7 represent the relationship between axialdisplacement for a 1 G sinusoidal vibration load for various materialproperties and fixed geometries. FIG. 6 shows that the dampingcoefficient does not effect the first modal frequency while FIG. 7 showsthe effects of axial displacement on the first modal frequency.Mechanical Input Properties for 130 mm ABA Co-Injected Disk StorageModulus Damping Poisson’s Structure Material (psi) Coefficient RatioS.G. Skin Neat Resin 3.15E + 05 0.033 0.385 1.200 Core Filled 1.25E + 060.040 0.375 1.315 System 1.25E + 06 0.060 0.375 1.320 1.25E + 06 0.0800.375 1.325 1.25E + 06 0.100 0.375 1.330

[0042] Damping, also referred to as dampening, can be achieved through avariety of approaches such as by addition of an energy absorbingcomponent or through slip mechanisms involving various fillers andreinforcing agents. Useful materials that may improve the dampingcharacteristics include elastic materials with high damping capabilities(e.g., a damping coefficient of greater than about 0.05), such asvulcanized rubbers, acrylic rubbers, silicone rubbers, butadienerubbers, isobutylene rubbers, polyether rubbers, isobutylene-isoprenecopolymers and isocyanate rubber, nitrile rubbers, chloroprene rubbers,chlorosulfonated polyethylene, polysulfide rubbers and fluorine rubber,block copolymers including polystyrene-polyisoprene copolymers such asdescribed in U.S. Pat. No. 4,987,194 (which is incorporated herein byreference), thermoplastic elastomeric materials, includingpolyurethanes, and combinations comprising at least one of theforegoing, among others. Vibration-damping materials also include resinsin which large amounts of particles (such as ferrites, metals, ceramicsand the like), flakes (such as of talc, mica and the like), and variousfibers (such as zinc oxide, wollastonite, carbon fibers, glass fibers,and the like), and mixtures comprising at least one of the foregoing,can be employed. Microfibers, fibrils, nanotubes, and whiskers, foamedand honeycombed structures may also be useful as are variouscombinations of the foregoing.

[0043] In addition to, or in place of, reducing axial displacementthrough the use of damping materials in the substrate, axialdisplacement can be reduced by utilizing a vibration damping material inthe restraining device, or clamping structure, that holds the substrate.The addition of visco-elastic materials to the clamp or between theclamp and substrate effectively reduces axial displacement of the diskcompared to the same structure without the additive. In one embodiment,the vibration-damping material should preferably have a dampingcoefficient higher than the damping coefficient of the disk substrate,and a modulus of elasticity high enough to reduce creep properties,e.g., a modulus of elasticity greater than about 20 kpsi. Usefulmaterials that may improve the damping characteristics of the clampinclude elastic materials with high damping capabilities, such asvulcanized rubbers, acrylic rubbers, silicone rubbers, butadienerubbers, isobutylene rubbers, polyether rubbers, isobutylene-isoprenecopolymers and isocyanate rubber, nitrile rubbers, chloroprene rubbers,chlorosulfonated polyethylene, polysulfide rubbers and fluorine rubber,block copolymers including polystyrene-polyisoprene copolymers such asdescribed in U.S. Pat. No. 4,987,1 94, thermoplastic elastomericmaterials, including polyurethanes, and combinations thereof, amongothers. Foamed or honeycomb structures can also be useful.

[0044] Other factors that effect the stability and life of the storagemedia relate to dimensional stabilities and hygrothermal properties. Asubstrate with thermal and moisture dimensional stabilities attemperatures within the storage and operating temperature range of thestorage media should be employed with thermal and moisture stabilitiesat temperatures of about −6° C. (21° F.) to about 40° C. (104° F.)typically acceptable, stabilities within temperatures of about −12° C.(10° F.) to about 80° C. (175° F.) preferred, and stabilities withintemperatures of about −16° C. (3° F.) about 100° C. (212° F.) especiallypreferred. Due to the varied environments in which the storage media maybe employed or stored, the storage media preferably has: (1) a heatdistortion temperature greater than about 60° C. (140° F.), with greaterthan about 80° C. preferred; (2) creep characteristics preferably equalto or better than that of bisphenol-A based polycarbonate resin; and (3)good hygrothermal properties such that the substrate does notsignificantly change shape, such as bow or warp. Preferably, thesubstrate's moisture content varies less than about 1.0% at equilibrium,with less than about 0.5% at equilibrium more preferred, and less thanabout 0.3% at equilibrium especially preferred, under test conditions of80° C. at 85% relative humidity after 4 weeks.

[0045] In order to address the above design issues, this substrate canbe homogenous or non-homogenous, and can have numerous geometries. Thehomogenous substrate can be a plastic, which is substantially solid ormay contain a varying degree of porosity or one or more cavities (seeFIGS. 15, 16, 17, and 33 to 35). As is illustrated in these Figures, thedensity of the substrate can be reduced by employing one or more hollowcavities (holes, bubbles, ribs, passageways, webs, etc.) within thesubstrate while maintaining a sufficiently smooth surface either bycontaining the cavities within the substrate or by utilizing a coatingover the substrate in the area of the storage media where the data willbe stored.

[0046] The size, shape, and location of the cavities is based upon theabove mentioned design criteria. For example, referring to FIG. 17, thecavities may be located near the outer diameter of the substrate suchthat the central area of the substrate, which may be secured to the hubof the media read/write system, has the maximum yield strength while theouter periphery of the substrate has reduced density and inertialissues. As can be seen in FIGS. 8 to 14, and 33 to 35, the cavity canhave various geometries (linear, curved, convex, concave,convexo-concave, concavo-concave, convexo-convex, and the like), sizes(width, length and height), and locations throughout the substrate(intermittent, from the inner diameter to the outer diameter, or anylocation therebetween), and can be interconnecting or separate.

[0047] The non-homogenous substrate can be a plastic with a filler,core, or other reinforcement or insert, or may be a composite material,or combinations thereof (see FIGS. 8 to 27). As is shown in the variousdrawings and as stated below in greater detail, the material geometry,location, and size of the insert/core/reinforcement can be adjusted toaddress the various design criteria; such as interconnecting orseparate, solid or non-solid, plates, web designs, hub designs,stiffening structures, inner diameter and/or outer diameter inserts,top, middle, bottom, or offset designs, finger or directional design,concentric stiffeners, partial surface, welded, bonded, or encapsulated;or combinations comprising at least one of the foregoing.

[0048] Referring to FIGS. 22 to 24, for example, a substrate can have areinforcement that comprises substantially all of the volume of thesubstrate such that the majority of the plastic is merely disposed nearthe surface of the substrate, e.g., as a thin film. In this embodiment,the core, which forms the majority of the substrate, can have athickness up to about 2.5 mm, with a thickness of about 0.75 mm to about2.0 mm preferred, and about 0.8 mm to about 1.2 mm especially preferred.As is illustrated, the thin plastic film can be disposed on one or bothsides of the core (e.g., metal, ceramic, glass, or the like). Typicallya plastic film having a thickness of about 50 μ or less can be employed,with a thickness of about 20 μ or less preferred.

[0049] Regardless of whether the substrate is homogenous ornon-homogenous, contains hollow or filled cavities, or reinforcement,its geometry as well as the geometry of the core/insert/reinforcement,can also be adjusted, interchangeably, to address various of the designfactors. Referring to FIGS. 8 to 35, various substrate and core/insertgeometries, respectively, include substantially constant thickness,tapering on one or both sides, convex or concave on one or both sides,or combinations comprising at least one of the foregoing.

[0050] Adjusting the geometry of the substrate enables manipulation ofthe moment of inertia of the substrate when rotating, and control of themodal responses, i.e. the harmonics thereof. For example, various modalshapes (as shown in FIG. 36) can be obtained and avoided, based uponsectional variations in density through planar and/or radial thickness.As stated above, the preferred design is a substrate having a firstmodal resonance frequency outside of the frequency range for which thestorage media is designed.

[0051] Another manner of addressing the various design criteria for thestorage media is addressing its use, such as its operating rotationalspeed which effects the speed in which data can be stored/retrieved.Conventionally, during use, storage media has been rotated at a constantspeed. The media is brought to its operating rotational speed prior toany reading or writing. However, the storage media can be rotated at avaried speed where the speed increases during peak use periods whiledecreasing during normal use periods; or rotational speed can be variedin order to maintain constant linear velocity at different areas of thedisk (e.g., inner vs. outer diameter). Such operating criteria will bothconserve energy and potentially render some design criteria moreimportant. Such criteria include, e.g., moment of inertia, modulus,density, viscoelasticity, thickness, and/or diameter to name a few.Storage media devices that change speeds make many of these criteria,e.g., moment of inertia and density, etc. of increased importance ascompared to constant speed devices.

[0052] In theory, any plastic that exhibits appropriate properties andcan be employed as the substrate, core, and/or coating. However, theplastic should be capable of withstanding the subsequent processingparameters (e.g., application of subsequent layers) such as sputtering(i.e. temperatures up to and exceeding about 200° C. (typically up to orexceeding about 300° C.) for magnetic media, and temperatures of aboutroom temperature (about 25° C.) up to about 150° C. for magneto-opticmedia). That is, it is desirable for the plastic to have sufficientthermal stability to prevent deformation during the deposition steps.For magnetic media, appropriate plastics include thermoplastics withglass transition temperatures greater than about 150° C., with greaterthan about 200° C. preferred (e.g., polyetherimides,polyetheretherketones, polysulfones, polyethersulfones,polyetherethersulfones, polyphenylene ethers, polyimides, high heatpolycarbonates, etc.); with materials having glass transitiontemperatures greater than about 250° C. more preferred, such aspolyetherimide in which sulfonedianiline or oxydianiline has beensubstituted for m-phenylenediamine, among others, as well as polyimides,such as Probimide (or the dry powder equivalent, Matrimid 5218, fromCiba Geigy Chemical); combinations comprising at least one of theforegoing, and others.

[0053] Additionally, it is possible for thermosets to be used in theapplication provided the thermoset possess sufficient flow under thestamping conditions to permit formation of the desired surface features.As various applications may require polymers with different glasstransition temperatures, it may be advantageous to be able to adjust theglass transition temperature of a plastic (homopolymer, copolymer, orblend) to achieve a film with the desired glass transition temperature.To this end, polymer blends, such as those described in U.S. Pat. No.5,534,602 (to Lupinski and Cole, 1996), may be employed in thepreparation of the coating solution. In this example, polymer blendsprovide, selectively, variable glass transition temperatures of about190° C. to about 320° C.

[0054] Some possible examples of plastics include, but are not limitedto, amorphous, crystalline and semi-crystalline thermoplastic materials:polyvinyl chloride, polyolefins (including, but not limited to, linearand cyclic polyolefins and including polyethylene, chlorinatedpolyethylene, polypropylene, and the like), polyesters (including, butnot limited to, polyethylene terephthalate, polybutylene terephthalate,polycyclohexylmethylene terephthalate, and the like), polyamides,polysulfones (including, but not limited to, hydrogenated polysulfones,and the like), polyimides, polyether imides, polyether sulfones,polyphenylene sulfides, polyether ketones, polyether ether ketones, ABSresins, polystyrenes (including, but not limited to, hydrogenatedpolystyrenes, syndiotactic and atactic polystyrenes, polycyclohexylethylene, styrene-co-acrylonitrile, styrene-co-maleic anhydride, and thelike), polybutadiene, polyacrylates (including, but not limited to,polymethylmethacrylate, methyl methacrylate-polyimide copolymers, andthe like), polyacrylonitrile, polyacetals, polycarbonates, polyphenyleneethers (including, but not limited to, those derived from2,6-dimethylphenol and copolymers with 2,3,6-trimethylphenol, and thelike), ethylene-vinyl acetate copolymers, polyvinyl acetate, liquidcrystal polymers, ethylene-tetrafluoroethylene copolymer, aromaticpolyesters, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidenechloride, Teflons, as well as thermosetting resins such as epoxy,phenolic, alkyds, polyester, polyimide, polyurethane, mineral filledsilicone, bis-maleimides, cyanate esters, vinyl, and benzocyclobuteneresins, in addition to blends, copolymers, mixtures, reaction productsand composites comprising at least one of the foregoing.

[0055] Filler/reinforcement/core materials can be any materialcompatible with the plastic and the ultimate environment in which thestorage media will be employed, which can be secured within or to theplastic, or which the plastic can be coated over, to produce the desiredsurface quality in the area of data storage, and which provides theadditional desired mechanical strength to the substrate. Possiblematerials include: glass (such as silica, low melt glasses, etc.), foamsand other low density materials, carbon, metals (such as aluminum, tin,steel, platinum, titanium, metal matrices, others and combinations andalloys comprising at least one of the foregoing), organic and inorganicmaterials, ceramics (e.g. SiC, Al₂ O₃, etc.) thermoplastics, thermosets,rubbers, among others and composites, alloys and combinations comprisingat least one of these materials. These materials can be in the form ofparticles, bubbles, microspheres or other hollow fillers, fibers (long,short, continuous, chopped, etc.), mesh, woven, non-woven, preforms,inserts, plates, disks, others and combinations comprising at least oneof the foregoing, of various sizes and geometries. For example, FIGS. 33to 35 show a few of the possible core/insert geometries with thepolymeric material comprising a thin (e.g., less than about 50 μ)coating or thick (e.g., greater than about 50 μ) coating over thecore/insert. Glass, metal, metal matrix composites, and carbon cores aretypically preferred for some applications where elevated temperaturesmay be a factor, due to the reduced thermal decay of stiffness insubstrates containing these materials.

[0056] The amount of filler employed is dependent upon the desiredsubstrate mechanical properties and the fillers effects on thesubstrates' harmonics, surface quality, and inertial factors. The filler(particles, cavity, bubbles, core, inserts, etc.) can occupy up to asmuch as 99.9% or more of the volume (vol %) of the substrate, with about5 vol % to about 50 vol % occupied by the filler more common, and about85 vol % to about 99 vol % occupied by the filler preferred in somealternate embodiments.

[0057] Numerous methods can be employed to produce the storage mediaincluding injection molding, foaming processes, sputtering, plasma vapordeposition, vacuum deposition, electrodeposition, extrusion coating,spin coating, spray coating, meniscus coating, data stamping, embossing,surface polishing, fixturing, laminating, rotary molding, two shotmolding, co-injection, over-molding of film, microcellular molding, aswell as other techniques, and combinations comprising at least one ofthe foregoing. Preferably the technique employed enables in situproduction of the substrate having the desired surface features, (e.g.,servo-patterning (such as pits and grooves), bit patterning, edgefeatures, protrusions, asperities (e.g., laser bumps, and the like),R_(a), etc.).

[0058] One possible process comprises an injection molding-compressiontechnique where a mold is filled with a molten plastic. The mold maycontain a preform, inserts, fillers, etc. The plastic is cooled and,while still in an at least partially molten state, compressed to imprintthe desired surface features (e.g., pits, grooves, edge features,smoothness, and the like), arranged in spiral concentric or otherorientation, onto the desired portion(s) of the substrate, i.e. one orboth sides in the desired areas. The substrate is then cooled to roomtemperature.

[0059] For optical or magnetic data storage on a substrate, informationstored is often stored on the surface of the substrate. This informationmay be imprinted directly onto the surface (as in the case of a CD), orstored in a photo- or magnetically-definable medium, which has beendeposited onto the surface of substrate (e.g., “Winchester” hard diskdrive). Due to the surface quality requirements of such systems, disks(metal, ceramic, glass, etc.) were coated with nickel phosphide (NiP),for example, and then polished to obtain the desired surface quality.However, polishing is an expensive and laborious process. Additionally,these substrates do not traditionally offer the capability of imprintingfeatures onto the surface, even though such features, e.g., pits orgrooves, may be desirable for use as geographic locators, such as asector map. Typically these geographic locators have a depth of up toabout 30 nanometers (nm) or more, with about 20 nm to about 30 nmgenerally preferred.

[0060] In one embodiment, a metal, glass, ceramic, or other substrate towhich a plastic layer has been applied exhibits both the desiredmechanical properties and the ability to have surface features imprintedinto the surface. The plastic layer can be deposited by a variety oftechniques, including spin coating, vapor deposition (e.g. plasmaenhanced chemical vapor deposition), electrodeposition coating, meniscuscoating, spray coating, extrusion coating, and the like, andcombinations comprising at least one of the foregoing.

[0061] Spin coating comprises preparing a solution of a plasticprecursor (e.g., monomer or oligomer) or the plastic itself (where asolvent can be employed, or one of the monomers can act as the solvent).The disk to be coated is secured to a rotatable surface and a portion ofplastic solution is dispensed near the center of the substrate.Alternately, a bead of the plastic solution is deposited in a ring likegeometry, along the inner boundary of disk where the coating is to belocated. The disk is then spun at a sufficient rate to, via centrifugalforces, spread the plastic solution across the surface of the disk.Finally, if applicable, the coating is dried and cured.

[0062] In order to improve adhesion of the coating to the substrate,optionally, an adhesion promoter, such as an organosilane or anotherconventional adhesion promoter, can be used. Possible organosilanesinclude VM-651 and VM-652 commercially available from DuPont. If anadhesion promoter is employed, it is typically dissolved in a solvent,such as methanol, water, and combinations comprising at least one of theforegoing, and is applied to the disk prior to applying the plasticbead. Once the adhesion promoter is spin coated onto the disk, theplastic coating is applied as described above.

[0063] For example, a polyetherimide resin, such as Ultem® resin grade1000, commercially available from GE Plastics, is dissolved inanisole/gamma-butyrolactone solvent system (15% Ultem® resin by weight(wt %)). A rigid substrate (metal, polymer, glass, or other), which isoptionally polished, is placed on a rotatable device, commonly referredto as a spinner, and held in place via a mechanical device or a vacuum.An adhesion promoter, such as 5 ml of 0.05% solution VM651 (an adhesionpromoter commercially available from DuPont) in water/methanol solution,is applied by dispensing it onto the spinning or stationary substrate.The substrate is then, preferably, spun to distribute the adhesionpromoter, such as at a rate of about 2,000 rpm for about 30 seconds. Ifan adhesion promoter is employed, the substrate can optionally berinsed, such as with methanol, to remove excess adhesion promoter, anddried (e.g., air dried, vacuum dried, heat dried, or the like), prior tothe application of the plastic solution.

[0064] Once the rigid substrate has been prepared, plastic solution canbe applied to the substrate around the inner diameter of the area to becoated, while optionally masking areas that are not to be coated. Thesubstrate is spun to substantially uniformly spread the plastic solutionacross the substrate, forming a film. The thickness of the film isdependent upon various parameters, e.g., the quantity of plasticsolution, the desired thickness, the viscosity of the plastic solution,the spin rate, the spin duration, plastic solution solids content, andenvironmental conditions (including temperature, humidity, atmospheretype (e.g. inert gas), and atmospheric pressure), among others. Althougha thickness below about 0.1 microns (μ) can be attained, the film ispreferably sufficiently thick to afford a planar surface overundesirable surface imperfections in the substrate and to allow desiredsurface features (e.g., pits, grooves, etc.) to be placed onto the film.Typically, a thickness of about 0.5 μ or greater is generally preferred,with a thickness of up to about 50 μ possible, up to about 20 μpreferred, and about 0.5 μ to about 10 μ especially preferred forstorage media type applications. Determination of a final thicknessrange will vary, in part, by the desired depth of any features to beplaced onto the film as well as the surface imperfections on the rigidsubstrate that need to be masked by the film.

[0065] With respect to spin duration and rate, which must be sufficientto disperse the plastic solution across the substrate in the desiredarea, these parameters are chosen based on factors including, e.g., theplastic solution viscosity and solids content, and the desired coatingthickness; all interdependent parameters. Typically, however, the spinrate is greater than about 1,000 revolutions per minute (rpm) for up toabout 5 minutes or more, with greater than about 1,500 rpm for less thanabout 2.5 minutes preferred, and greater than about 1,800 rpm for lessthan about 1.5 minutes especially preferred. For example, a 3 μ thickcoating can be applied using plastic solution containing 15 wt % Ultem®resin grade 1000 in anisole/gamma-butyrolactone solvent, and a spin rateof 2,000 rpm for a duration of 25 seconds.

[0066] Once the coating as been dispersed across the substrate, it canbe cured, preferably in an inert atmosphere, such as nitrogen, for asufficient period of time to remove the solvent and polymerize thepolymer precursor (if necessary) and at a rate effective to obtain thedesired surface quality. The coated substrate can be raised to thedesired temperature at a rate such that the solvent removal doesn't havedeleterious effects on the surface features. For example, the coatedsubstrate can be heated to greater than about 200° C., with about 300°C. or greater typically preferred, at a rate of up to about 10 degreesper minute (deg/min), with a rate of up to about 5 deg/min preferred,and a rate of less than about 3 deg/min especially preferred. Once thesubstrate has attained the desired temperature, it is maintained at thattemperature for a sufficient period of time to remove the solvent and,if necessary, to polymerize the polymer precursor, and is then cooled.Typically a period of up to several hours is employed, with less than 2hours preferred, and a rate of minutes or portions thereof especiallypreferred. A substrate prepared in this manner, optionally withsubsequent processing, can be used for data storage applications, suchas magnetic hard drives.

[0067] Alternatively, the substrate (entire substrate or coating on thecore) can be cured using microwave technology. Preferably, a variablefrequency microwave curing system is employed. The substrate enters themicrowave area where the sweep rate, power, bandwidth, and centralfrequency are adjusted for the particular substrate such that themicrowave selectively heats the polymer without substantially effectingthe core, if desired.

[0068] Other possible curing techniques include using ultraviolet lightto initiate a crosslinking reaction, radiative heating (placing thesample in close proximity to a hot surface), contact heating (sample isin physical and therefore thermal contact with a hot fixture), rapidthermal annealing (employing a heat source such as a coil or the like,or a lamp such as quartz or the like, which is heated at a very rapidrate, such as greater than 10 degrees per second), inductive heating(e.g., with radio frequency), and the like, as well as combinationscomprising at least one of the foregoing.

[0069] In conjunction with the above curing techniques, other processingmethods may be employed to facilitate the curing process, to removesolvent, and/or to improve the quality of the product. Possibleadditional processing methods include: employing a vacuum, usingstripping agents (e.g., inert gasses, inert volatile solvents,azeotropes, and the like), drying agents, and other conventionalmethods, as well as combinations comprising at least one of theforegoing.

[0070] Alternatively, the curing time can be based upon economies andthe desired surface features (pits, grooves, asperities (e.g. laserbumps), edge features, and/or smoothness) can be disposed on the surfacesubsequent to curing. Following application, if applicable, the plasticfilm is cured (thermal, ultraviolet, etc.), and, optionally, the desiredsurface features are formed by photolithography (including, but notlimited to dry etch), laser ablation through direct write or wideexposure with the use of photomasks, hot or cold stamping, embossing, orother techniques.

[0071] Putting the surface features on the substrate by employingphotolithography can be accomplished with any conventionalphotolithography technique, such as those which employ reactive ionetching, plasma, sputtering, and/or liquid chemicals or chemical vaporsto etch the polymer coating. Conventional photolithographic techniques,e.g., nanoimprint lithography, used to prepare contact probe datastorage devices are useful; however, care must be taken to retainsufficient plastic film depth within the surface feature to provide thedesired planarity of the surface of the rigid substrate.

[0072] Generally, embossing is preferred since the substrate is eitherplastic or at least comprises a thin plastic film on the embossingsurface. Not to be limited by theory, due to the rheology of the plasticmaterial, not only can pits, grooves, and edge features be embossed intothe substrate, but the desired surface quality can also be embossed(e.g., desired smoothness, roughness, microwaviness, and flatness). In apreferred embodiment, embossed bit-patterns and/or servo-patterns have adepth of about 10 nm to about 150 nm, preferably about 20 nm to about 50nm. Depths shallower than about 10 nm can result in features that arenot accurately recognized by the head device. Conversely, deeperfeatures or features that vary outside the ranges can result inundesirable head-disk interactions.

[0073] Embossing, can be accomplished using conventional techniques.Alternatively, a unique embossing technique can be employed where asubstrate, such as a disk having a plastic surface, is embossed bypreheating a mold. The mold should be heated to a temperature that, inconjunction with the temperature of the substrate, is capable ofembossing the desired surface features onto the plastic surface of thesubstrate. The mold temperature can be at, above, or below the glasstransition (Tg) temperature of the material to be embossed. If thetemperature is above such glass transition temperature, it is preferredthe mold temperature be within about 30° C. of the glass transitiontemperature of the material, with a temperature within about 15° Cpreferred, and a temperature within about 10° C. especially preferred;with the mold being preheated to a temperature below the glasstransition temperature of the material to be embossed even morepreferred. In an especially preferred embodiment, the mold is preferablyheated to within a few degrees below the glass transition temperaturefor crystalline materials, and at a temperature within at least about 5°C., preferably within at least about 10° C. or greater for amorphousmaterials.

[0074] In addition to heating the mold, the substrate is heated to atemperature greater than the glass transition temperature of thematerial to be embossed. The substrate is heated to the materialtemperature required to facilitate replication of the geographiclocators and/or other surface features on the substrate. Typically, thesubstrate is heated to about 5° C. above the glass transitiontemperature or less for crystalline material, with greater than about 5°C. common for amorphous materials.

[0075] Once the substrate has attained the desired temperature, it isplaced in the mold and pressure is applied. After placing the substratein the mold the temperature thereof can be maintained, increased ordecreased as necessary in order to optimize replication and enablesubstrate release from the mold while maintaining the integrity of thesurface features. Typically in order to maintain the integrity of thesurface features, the molded substrate is cooled to below the glasstransition temperature prior to removal from the mold.

[0076] By preheating to and maintaining the mold at a temperature belowthe glass transition temperature of the material, the time required forheat-up and cool-down of conventional embossing processes issignificantly diminished, especially in relation to processing numeroussubstrates. For example, numerous substrates are heated to a temperatureabove the glass transition temperature of the material to be embossed.Meanwhile the mold is heated to and maintained at a temperature belowthe glass transition temperature. A substrate is then placed in the moldand is embossed while the mold cools the substrate (due to thetemperature differential). The substrate can then be removed from themold and the next substrate placed in the mold. It is not necessary toheat the substrate and the mold to above the glass transitiontemperature and then to cool the combination to below the glasstransition temperature as is conventional. Conventional embossingtechniques typically take about 6 to 12 hours to complete, while theabove embossing techniques can be accomplished in minutes.

[0077] For example, an aluminum disk coated with polyetherimide (Ultem®resin grade 1010) is fixtured to a spindle and heated to about 780° F.(415° C.) in a furnace oven. An embossing mold having the desiredsurface feature negative is heated to about 205° C. Once the disk is attemperature it is loaded into the mold and, while cooling (due to thetemperature of the mold) compressed under a time-pressure profile toemboss the surface features into the substrate surface. The embossedsubstrate is then removed from the mold.

[0078] By maintaining the mold below or slightly above the glasstransition temperature and separately heating the substrate to greaterthan the glass transition temperature, the embossing cycle time can bereduced by orders of magnitude.

[0079] Once the substrate has been coated with polymer, and formed withthe appropriate surface features, if desired various layers can then beapplied to the substrate through one or more conventional techniques,e.g., sputtering, chemical vapor deposition, plasma-enhanced chemicalvapor deposition, reactive sputtering, evaporation, and the like. Forexample, in some cases, high areal density storage media might have pitsand grooves on the polymer substrate that can be solely geographiclocators; i.e. they are not required to store data therein. The data isstored in data storage layer(s). Furthermore, the data stored in thedata storage layer(s) may be changed (rewritten) by repeating theimpinging step at higher densities than conventional, i.e. “low” densitycompact disks.

[0080] The layers applied to the substrate may include one or more datastorage layer(s) (e.g., magnetic, magneto-optic, etc.), protectivelayer(s), dielectric layer(s), insulating layer(s), combinations thereofand others. The data storage layer(s) may comprise any material capableof storing retrievable data, such as an optical layer, magnetic layer,or more preferably a magneto-optic layer, having a thickness of up toabout 600 Å, with a thickness up to about 300 Å preferred. Possible datastorage layers include, but are not limited to, oxides (such as siliconeoxide), rare earth element—transition metal alloy, nickel, cobalt,chromium, tantalum, platinum, terbium, gadolinium, iron, boron, others,and alloys and combinations comprising at least one of the foregoing,organic dye (e.g., cyanine or phthalocyanine type dyes), and inorganicphase change compounds (e.g., TeSeSn or InAgSb). Preferably, the datalayer has a coercivity of at least about 1,500 oersted, with acoercivity of about 3,000 oersted or greater especially preferred.

[0081] The protective layer(s), which protect against dust, oils, andother contaminants, can have a thickness of greater than 100 μ to lessthan about 10 Å, with a thickness of about 300 Å or less preferred insome embodiments. In another embodiment, a thickness of about 100 Å orless is especially preferred. The thickness of the protective layer(s)is usually determined, at least in part, by the type of read/writemechanism employed, e.g., magnetic, optic, or magneto-optic.

[0082] Possible protective layers include anti-corrosive materials suchas nitrides (e.g., silicon nitrides and aluminum nitrides, amongothers), carbides (e.g., silicon carbide and others), oxides (e.g.,silicon dioxide and others), polymeric materials (e.g., polyacrylates orpolycarbonates), carbon film (diamond, diamond-like carbon, etc.) amongothers, and combinations comprising at least one of the foregoing.

[0083] The dielectric layer(s) which are often employed as heatcontrollers, can typically have a thickness of up to or exceeding about1,000 Å and as low as about 200 Å.

[0084] Possible dielectric layers include nitrides (e.g., siliconnitride, aluminum nitride, and others); oxides (e.g., aluminum oxide);carbides (e.g., silicon carbide); and combinations comprising at leastone of the foregoing, among other materials compatible within theenvironment and preferably, not reactive with the surrounding layers.

[0085] The reflective layer(s) should have a sufficient thickness toreflect a sufficient amount of energy to enable data retrieval.Typically the reflective layer(s) can have a thickness of up to about700 Å, with a thickness of about 300 Å to about 600 Å generallypreferred. Possible reflective layers include any material capable ofreflecting the particular energy field, including metals (e.g.,aluminum, silver, gold, titanium, and alloys and mixtures comprising atleast one of the foregoing, and others). In addition to the data storagelayer(s), dielectric layer(s), protective layer(s) and reflectivelayer(s), other layers can be employed such as lubrication layer andothers. Useful lubricants include fluoro compounds, especially fluorooils and greases, and the like.

[0086] One unexpected result of the storage media described herein thatcontain a rigid substrate, e.g., an aluminum substrate, with a plasticresin embossed with surface features, was retention of head slapperformance as compared to conventional storage media. Conventionalaluminum media are typically coated, e.g., with nickel phosphide, toimprove the surface hardness for polishing and to resist damage to thepolished surface by contact with the head. Plastic resins are generallysofter than the aluminum surface coating and would be expected to limitthe head slap resistance of the storage media; however, storage mediadescribed herein containing plastic films unexpectedly exhibited noobserved diminished slap resistance. This unexpected result is believedto depend somewhat on the thickness of the plastic film and plasticfilms having higher thickness are expected to have diminished head slapresistance. Thus, in an especially preferred embodiment, the head slapresistance of a coated aluminum substrate having a plastic film,preferably containing surface features, is substantially equivalent tothe head slap resistance of the coated aluminum substrate not containingthe plastic film. Similar head slap results can be obtained with otherrigid substrates such as glass.

[0087] The storage media described herein can be employed inconventional optic, magneto-optic, and magnetic systems, as well as inadvanced systems requiring higher quality storage media and/or arealdensity. During use, the storage media is disposed in relation to aread/write device such that energy (magnetic, light, a combinationthereof or another) contacts the data storage layer, in the form of anenergy field incident on the storage media. The energy field contactsthe layer(s) disposed on the storage media prior to (if ever) contactingthe substrate. The energy field causes some physical or chemical changein the storage media so as to record the incidence of the energy at thatpoint on the layer. For example, an incident magnetic field might changethe orientation of magnetic domains within the layer, or an incidentlight beam could cause a phase transformation where the light heats thematerial.

[0088] For example, referring to FIG. 2, in a magneto-optic system 100,data retrieval comprises contacting the data storage layer(s) 102 with apolarized light 110 (white light, laser light, or other) incident onsuch layer(s). A reflective layer 106, disposed between the data storagelayer 102 and substrate 108, reflects the light back through the datastorage layer 102, the protective layer 104, and to the read/writedevice 112 where the data is retrieved.

[0089] In another embodiment, referring to FIG. 3, the read/write device112 detects the polarity of magnetic domains in the disk storage layer102′ (i.e. data is read). To write data onto the storage media, amagnetic field is imposed onto the data storage layer 102′ by theread/write device 112. The magnetic field passes from the read/writedevice 112′, through the lubrication layer 105, and the protective layer104 to the magnetic layer 102′, forming magnetic domains aligned ineither of two directions and thereby defining digital data bits.

[0090] The following examples are provided to further illustrate thepresent invention and are not intended to limit the scope thereof.

EXAMPLE 1

[0091] A substrate with outer diameter of 130 mm and thickness of 1.2 mmwas formed out of a polyetherimide resin (Ultem® resin grade 1010obtained from GE Plastics) using injection molding under standardconditions known in the art. The surface smoothness of the substrate wasless than 10 Å R_(a), and the first modal frequency was about 175 Hz. Atthis frequency, the axial displacement was about 0.889 mm.

[0092] The benefits compared to the prior art (Comparative Example #1)are clear.

EXAMPLE 2

[0093] A substrate with dimensions of 130 mm diameter and 1.2 mmthickness can be produced by injection molding of polycarbonate filledwith 20 wt % carbon fiber. The material will exhibit a flexural modulusof 1.6 million psi, a mechanical damping coefficient of 0.015, andspecific gravity of 1.29 g/cc. The storage media will demonstrate amaximum axial displacement of 0.32 mm during vibrational excitation, anda first modal frequency of 302 Hz.

EXAMPLE 3

[0094] A substrate with outer diameter of 95 mm and thickness of 2 mmwas formed with a core of polyphenylene ether/polystryrene (PPE/PS)containing 20 wt % ceramic microfibers and a skin of PPE/PS (40/60) byco-injection molding. The microfibers, with average dimensions on theorder of 10-20 μ length×0.3-0.6 μ diameter) were significantly smallerthan conventional carbon fibers. The surface smoothness of the substratewas improved by approximately a factor of 2 compared to the conventionalcarbon fiber co-injected disk and the first modal frequency was about425 Hz. At this frequency, the axial displacement was about 0.15 mm. Thebenefits compared to the prior art (Comparative Examples #1) are clear.

EXAMPLE 4

[0095] A substrate with outer diameter of 130 mm and thickness of 1.2 mmwas formed with a core of 20 wt % carbon fiber-filled polycarbonate anda skin of pure polycarbonate using co-injection molding with a thicknessratio of about 1 unit of core to 1 unit of skin under standardconditions known in the art. The surface smoothness of the substrate wasabout 10 Å R_(a) and the first modal frequency was about 210 Hz. At thisfrequency, the axial displacement was about 1.27 mm; however, thedisplacement and frequency can be changed with changes in the core toskin ratio. The benefits compared to the prior art (Comparative Example#1) are clear.

EXAMPLE 5

[0096] A substrate with outer diameter of 120 mm and thickness of 0.9 mmis formed out of polycarbonate containing 30 wt % carbon fiber, 21 wt %poly(styrene-isoprene), and 3.5 wt % poly(styrene-maleic anhydride) (allbased upon the total weight of the composition) using injection moldingusing standard conditions known in the art. The first modal frequency isabout 292 Hz. At this frequency, the axial displacement is about 0.069mm. The benefits compared to the prior art (Comparative Examples #1 and#2) are clear.

EXAMPLE 6

[0097] A substrate with outer diameter of 95 mm and thickness of 2 mm isformed with a core of polycarbonate containing 30 wt % carbon fiber, 21wt % poly(styrene-isoprene) vibration dampening filler, and 3.5 wt %poly(styrene-maleic anhydride) and skin of polycarbonate (all based uponthe total weight of the composition) using co-injection molding understandard conditions known in the art. The core comprises about 50% ofthe thickness of the disk. The surface smoothness of the substrate isabout 1.3 nm R_(a) and the first modal frequency is about 450 Hz. Atthis frequency, the axial displacement is about 0.033 mm. The benefitscompared to the prior art (Comparative Examples #1 and #2) are clear.

EXAMPLE 7

[0098] A substrate with outer diameter of 130 mm and thickness of 1.2 mmis formed with a core of polycarbonate containing 20 wt % carbon fiberand 10 wt % poly(styrene-isoprene) (all based upon the total weight ofthe composition) and a skin of polycarbonate by injection molding thefilled material in a mold that contains polycarbonate film on one orboth sides of the mold. The surface smoothness of the substrate is about1 nm R_(a) and the first modal frequency is about 250 Hz. At thisfrequency, the axial displacement is about 0.20 mm. The benefitscompared to the prior art (Comparative Examples #1 and #2) are clear.

EXAMPLE 8

[0099] A substrate with outer diameter of 130 mm and thickness of 1.2 mmis formed with a core of polycarbonate containing 30 wt % carbon fiberin a mold that contains polycarbonate film on one or both sides of themold. The surface smoothness of the substrate is about 1 nm R_(a) andthe first modal frequency is about 300 Hz. At this frequency, the axialdisplacement is about 0.40 mm. The benefits compared to the prior art(Comparative Example #1) are clear.

EXAMPLE 9

[0100] A thin layer (5 μ) of polyetherimide was electrochemicallydeposited onto one or both sides of an aluminum substrate. Subsequently,geographic locators (pits) were formed into the surface of thepolyetherimide film using a hot stamping technique. This substrate wassuperior to a traditional aluminum substrate (Comparative Example #2) inthat it contains the desirable pit structure of geographic locators andother surface features formed through embossing.

EXAMPLE 10

[0101] A thin layer of polyetherimide (5 μ) was deposited by spincoating a polymer containing solution onto one side of an aluminumsubstrate. This substrate was superior to a traditional aluminumsubstrate (Comparative Example #2) in that the final surface was smoothenough (less than 10 Å R_(a) and total surface flatness less than 8 μ)for use in magnetic data storage applications, but the substrate did nothave to undergo the plating and polishing steps used in the preparationof conventional metal or ceramic substrates. Upon deposition of asputtered magnetic data layer, magnetic coercivity greater than 2,500oersted was achieved.

EXAMPLE 11

[0102] A thin layer of polyetherimide (5 μ) was deposited by spincoating a polymer containing solution onto one side of a glasssubstrate. The final surface had less than 10 Å R_(a) and total surfaceflatness less than 8 μ. Upon deposition of a sputtered magnetic datalayer, magnetic coercivity greater than 3,000 oersted was achieved. Thecoated substrate showed no damage after a standard 800 G head slap test.

EXAMPLE 12

[0103] A thin layer of polyetherimide can be deposited by spin coating apolymer containing solution onto one or both sides of an aluminum-boroncarbide rigid substrate. This substrate would be superior to atraditional aluminum substrate (Comparative Example #2) in that thematerial would have a significantly higher specific modulus. It would besuperior to aluminum-boron carbide substrates without a coating in thatthe coating makes the surface smooth enough for use in magnetic datastorage applications. (Using conventional means, such as polishing, itis difficult, if not impossible, to achieve adequate surfacesmoothness.)

EXAMPLE 13

[0104] A thin layer of polyetherimide was deposited onto one side of analuminum substrate by spin coating a polymer-containing solution ontothe surface(s) and curing. Subsequently, surface features were formedinto the surface using an embossing technique, e.g., a hot stamping.This substrate was superior to a traditional aluminum substrate(Comparative Example #2) in that it contained the desirable pitstructure of geographic locators and the desired surface quality; e.g.,less than 10 Å R_(a).

EXAMPLE 14

[0105] A substrate with outer diameter of 130 mm and thickness of 1.2 mmand containing microporosity can be formed out of polycarbonate (Lexan®resin grade OQ1030L obtained from GE Plastics) using the Mucellmicrocellular injection molding process. The substrate would show 20%lower moment of inertia and higher modal frequency compared toComparative Example #1.

EXAMPLE 15

[0106] A substrate with outer diameter of 130 mm and thickness of 1.2 mmand containing a microporous and smooth polycarbonate skin can be formedout of polycarbonate (Lexan® resin grade OQ1030L obtained from GEPlastics) using the Mucell microcellular injection molding process in amold that contains polycarbonate film on one or both sides of the mold.The substrate would demonstrate the same benefits of reduced moment ofinertia and higher modal frequency of Example #13 with reduced surfaceroughness.

EXAMPLE 16

[0107] A substrate with outer diameter of 130 mm and thickness of 1.2 mmwas formed out of polyetherimide (Ultem resin grade 1010 obtained fromGE Plastics) filled with about 60 wt % of a low melting (less than 400°C.) glass filler (Corning Cortem) using injection molding under standardconditions known in the art. The first modal frequency was about 210 Hz.At this frequency, the axial displacement was about 0.723 mm. Thebenefits compared to the prior art (Comparative Example #1) are clear.

EXAMPLE 17

[0108] A substrate with outer diameter of 120 mm and thickness of 1.2 mmwas formed out of styrene-acrylonitrile copolymer (SAN CTS100 obtainedfrom GE Plastics) using injection molding under standard conditionsknown in the art. The substrate showed reduced moment of inertia,improved flatness, and higher modal frequency compared to ComparativeExample #1.

EXAMPLE 18

[0109] A substrate with outer diameter of 120 mm and thickness of 1.2 mmwas formed out of a 60/40 weight percent blend of poly(phenylene ether)resin and polystyrene using injection molding. The substrate showedreduced moment of inertia, improved flatness, and higher modal frequencycompared to Comparative Example 1.

EXAMPLE 19

[0110] A substrate with outer diameter of 120 mm and thickness of 1.2 mmcan be formed out of a 45/30/25 weight percent blend of poly(phenyleneether) resin, polystyrene, and polystyrene-co-(acrylonitrile) usinginjection molding. The substrate will show reduced moment of inertia,improved flatness, and higher modal frequency compared to ComparativeExample #1.

EXAMPLE 20

[0111] A substrate with outer diameter of 120 mm and thickness of 1.2 mmout of a 60/40 wt % blend of poly(phenylene ether) resin withpolystyrene and containing 20 wt % of zinc sulfide particulate filler(all weights based on the weight of the entire composition) usinginjection molding. The substrate showed reduced moment of inertia,improved flatness, and higher modal frequency compared to ComparativeExample #1.

EXAMPLE 21

[0112] A substrate with outer diameter of 120 mm and thickness of 1.2 mmwas formed out of a 60/40 weight percent blend of poly(phenylene ether)resin with polystyrene and containing 20 wt % of clay particulate filler(all weights based on the weight of the entire composition) usinginjection molding. The substrate showed reduced moment of inertia,improved flatness, and higher modal frequency compared to ComparativeExample #1.

EXAMPLE 22

[0113] A substrate with outer diameter of 120 mm and thickness of 1.2 mmcan be formed out of a 60/40 weight percent blend of poly(phenyleneether) resin with polystyrene and containing 20 wt % of zinc sulfideparticulate filler (all weights based on the weight of the entirecomposition) using injection molding in a mold containing a “managedheat transfer” insulating layer, as described in U.S. Pat. No.5,458,818. The substrate would show reduced moment of inertia, improvedflatness, and higher modal frequency compared to Comparative Example #1and improved replication of the mold surface compared to Example #20.

EXAMPLE 23

[0114] A substrate can be prepared as in Example #15. The substrate washeld using a clamping device that contained a viscoelastic washer (e.g.,elastomer) between the mount and the substrate. The structure showedreduced axial displacement (0.475 mm vs. 0.723 mm) at the first modalfrequency compared to the same substrate when clamped using a device notcontaining the elastomeric washer.

Comparative Example 1

[0115] A substrate with outer diameter of 130 mm and thickness of 1.2 mmwas formed out of a polycarbonate resin (Lexan® resin grade OQ1030Lobtained from GE Plastics) using injection molding. The surfacesmoothness of the substrate was less than about 10 Å R_(a) and the firstmodal frequency was about 150 Hz. At this frequency, the axialdisplacement was about 1.40 mm.

Comparative Example 2

[0116] A substrate with outer diameter of 130 mm and thickness of 1.2 mmwas formed out of aluminum by punching the disk from an aluminum sheet,plating with nickel-phosphide, and polishing to achieve the desiredsurface roughness (less than 10 Å R _(a)). The first modal frequency wasabout 500 Hz. At this frequency, the axial displacement was about 0.075mm.

[0117] It should be clear from the examples and teachings providedherein that novel and/or enhanced storage media for data have beeninvented. In some embodiments, optical, magnetic, and/or magneto-opticalmedia that are at least in part made from plastic and having a highstorage capability, e.g., areal density greater than about 5 Gbits/in ,can be designed. In other embodiments, storage media were unexpectedlyprovided having very desirable properties, including at least one of,e.g., surface roughness of less than about 10 Å R_(a), lowmicrowaviness, edge-lift less than about 8 μ, mechanical dampingcoefficient greater than about 0.04 at a temperature of 24° C., aresonant frequency of greater than about 250 Hz, an axial displacementpeak of less than about 500 μ under shock or vibration excitation, adata layer with a coercivity of at least about 1,500 oersted, and aYoungs modulus of at least about 7 GPa.

[0118] Some of the storage media described herein contain a rigid corewith a spin coated, spray coated, electrodeposited, or combinationthereof, plastic film or layer on one or both sides. The plastic may bea thermoplastic, thermoset, or mixture thereof. In additionalembodiments, the storage media has surface features (e.g., pits,grooves, edge features, asperities (e.g., laser bumps, and the like),roughness, microwaviness, and the like) placed into the plastic (film,layer, core, substrate) preferably using an embossing technique (i.e.,the substrate can be physically patterned). A further advantage of aphysically patterned substrate is the elimination of the need forservo-patterning (pits, grooves, etc.) of the data layer. This caneliminate the time consuming process of servo-patterning the data layer;typically a several hour process. In addition, since the data layer canbe wholly or substantially free of servo-patterning, the area of thedata layer available for data storage is increased.

[0119] Unexpected results were also obtained in relation to furtherprocessing and mechanical properties. As is discussed above, the plasticwithstood the deposition of additional layers (e.g., data layer(s),reflective layer(s), protective layer(s), etc.) using techniques such assputtering at elevated temperatures, often at temperatures in excess ofthe glass transition temperature of the plastic. Also, the hybridstorage media containing a rigid substrate having a plastic film orlayer attached thereto retained head slap performance as compared toconventional storage media. These illustrative embodiments and resultsshould be apparent to those of ordinary skill in the art from thedescription and examples provided herein.

[0120] Unlike prior art storage media, this storage media employs asubstrate having at least a portion thereof plastic (e.g., at least athin plastic film) to attain the desired mechanical properties andsurface features. Due to the use of the plastic, in situ formation ofthe substrate with the desired surface features is possible.Furthermore, surface features, including roughness, etc., can beembossed directly into the substrate surface, rendering production ofthis storage media cost effective. A further advantage is that thesurface features have a greater than about 90% replication of anoriginal master.

1. A storage media for data, said media comprising: a substrate; atleast one plastic film; and at least one data layer disposed on saidplastic film; wherein said data layer can be at least partly read from,written to, or a combination thereof by at least one energy field; andwherein said energy field comprises at least one of an electric field, amagnetic field, and an optical field.
 2. The storage media as in claim1, wherein said rigid substrate has a Young's modulus of at least about7 GPa.
 3. The storage media as in claim 2, wherein said Young's modulusis at least about 70 GPa.
 4. The storage media as in claim 3, whereinsaid Young's modulus is at least about 200 GPa.
 5. The storage media asin claim 1, wherein said substrate comprises at least one of metal,glass, ceramic, reinforced plastic, or combinations comprising at leastone of the foregoing.
 6. The storage media as in claim 1, wherein saidplastic film comprises embossed surface features.
 7. The storage mediaas in claim 1, wherein said plastic film comprises embossed surfacefeatures selected from the group consisting of pits, grooves, edgefeatures, asperities, and combinations comprising at least one of theforegoing.
 8. The storage media as in claim 1, wherein said rigidsubstrate comprises a glass substrate.
 9. The storage media as in claim1, wherein the head slap characteristics of the storage media containingthe at least one plastic film is substantially equivalent to a secondstorage media not containing the at least one plastic film.
 10. Thestorage media as in claim 1, wherein said storage media has a data layerwith a coercivity of at least about 1,500 oersted.
 11. The storage mediaas in claim 1, wherein said storage media has a data layer with acoercivity of at least about 3,000 oersted.
 12. The storage media as inclaim 1, comprising at least one spin coated, spray coated, or spin andspray coated plastic film.
 13. The storage media as in claim 1, whereinsaid plastic film comprises a thermoplastic resin with a glasstransition temperature of at least 140° C.
 14. The storage media as inclaim 1, wherein said plastic film comprises at least one thermoplasticresin of the group consisting of polyetherimides, polyetheretherketones,polysulfones, polyethersulfones, polyetherethersulfones, polyphenyleneethers, thermoplastic polyimides, and polycarbonates.
 15. The storagemedia as in claim 1, wherein said plastic film comprises at least onethermoset resin comprising embossed surface features.
 16. The storagemedia as in claim 1, wherein said plastic film comprises at least onethermoset resin, wherein the at least one thermoset resin at leastpartially cured during a process to emboss surface features onto the atleast one thermoset resin.
 17. The storage media as in claim 1, whereinsaid plastic film comprises at least one thermoset resin selected fromthe group consisting of epoxy, phenolic, alkyds, polyester, polyimide,polyurethane, mineral filled silicone, bis-maleimides, cyanate esters,vinyl, and benzocyclobutene resins.
 18. The storage media as in claim 1,wherein said thickness is about 0.82 mm to about 1.25 mm.
 19. A storagemedia, comprising: a substrate having a top side and a bottom side; atleast one plastic film on each of said top side and said bottom side;and at least one data layer disposed on at least one of said plasticfilm on each of said top side and said bottom side; and wherein saiddata layer can be at least partly read from, written to, or acombination thereof by at least one energy field; and wherein saidenergy field comprises at least one of an electric field, a magneticfield, and an optical field.
 20. A storage media for data, said mediacomprising: a substrate comprising an areal density greater than about10 Gbits/in² and an axial displacement peak of less than about 500 μunder shock excitation; at least one plastic film comprising a surfaceroughness of less than about 10 Å and at least one data layer disposedon said plastic film; wherein said data layer can be at least partlyread from, written to, or a combination thereof by at least one energyfield; and wherein said energy field comprises at least one of anelectric field, a magnetic field, and an optical field.